Performance Study Of 1Pt-yNi/Ni_0.05Ce_0.95-xZr_xO₂ Bimetallic Catalyst-Catalyzed CO₂ Methanation Reaction

The combustion of fossil fuels has increased atmospheric CO₂ emissions during the industrial period,which is one of the primary drivers of the global greenhouse effect,so CO₂treatment is required.In the framework of the carbon-neutral era,there is a growing emphasis on CO₂ reduction and recycling.Among the several ways for CO₂ reduction and recycling,the conversion of CO₂ to CH₄ has garnered the most attention,and catalytic CO₂ methanation is the favored alternative.In this paper,soft template agent poly（methyl methacrylate）（PMMA）was used,and Ni-doped 1Pt-y Ni/Ni_0.05Ce_0.95-xZr_xO₂ bimetallic series catalysts in ceria-zirconia solid-solution carrier were prepared by impregnation method and used for catalytic CO₂methanation reaction.The structure and performance of the catalysts were characterized by XRD,TEM,SEM,BET,H₂-TPR,CO₂-TPD,H₂-TPD,XPS,etc.The incorporation of Ni into the cerium-zirconium solid solution lattice improved the synergistic interaction between Ni and the solid solution carrier Ce element,and the percentage of effective basic sites on the catalyst surface increased from 8.87%at 5 mol.%Ni doping to29.39%at 20 mol.%Ni doping;and Ni-doped in ceria-zirconia solid solution with the same Ce/Zr ratio would have more surface active oxygen compared to Ni loaded on a ceria-zirconia solid solution with the same Ce/Zr ratio with the same molar ratio,from 17.31%to 20.34%.It boosted the catalytic efficiency of a low-temperature CO₂ methanation catalyst;the transfer of electrons between the doped Ni in the carrier and the loaded Pt led to an increase in the percentage of Ni0,which was more favorable for the CO₂ methanation reaction.The main intermediate of the CO₂ methanation process was formate;CO₂ interacted with-OH in Ce（OH）_x to create bidentate bicarbonate species and incoming H₂ was dissociated into reactive H atoms by Pt and Ni atoms.The bidentate bicarbonate would combine with the dissociated H atoms to generate formate,which would then react with more H to form methane.By varying the carrier Ce/Zr ratio,carrier Ni doping,and surface Ni loading,the influence of each factor on the catalytic performance of CO₂ methanation was examined.The Pt and Ni loadings were both one weight percent,the carrier was Ni_0.05Ce_0.85Zr_0.1O₂,the airspeed（GHSV）was 15,000 h^-1,and the CH₄ production at 350°C under atmospheric pressure was 68.85%,66.67%conversion,and 87.5%selectivity at 350°C.The experimental results revealed that a high Ce/Zr ratio was beneficial in enhancing the synergistic effect between the active component and the carrier,the catalyst H₂-TPR temperatures were 258°C and 356°C,the oxygen content on the catalyst surface reached 83.65%,and the H₂ adsorption on the catalyst surface was 22.3μmol/g,which significantly improved the catalyst CO₂ methanation performance,thus the 1Pt-1Ni/Ni_0.05Ce_0.85Zr_0.1O₂ catalyst showed excellent catalytic performance.